The objectives of this project are to assess changes in properties (number, affinity) of receptors in response to alterations in the environment, drug administration, stress, or hormones, and to develop methods for assessing receptor function in intact animals, in vivo. This year studies on the role of prostaglandins in regulation of blood pressure implicated in the pathogenesis of the hypertension in experimental animals have continued. Studies of responses in intact, awake animals provide a necessary complement to studies in pithed rats. Studies on the modes of action of phencyclidine and lithium which involved dopamine receptor changes have been examined.